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1.
Mem. Inst. Oswaldo Cruz ; 107(7): 916-922, Nov. 2012. ilus, mapas, tab
Article in English | LILACS | ID: lil-656049

ABSTRACT

In Brazil, decades of dengue vector control using organophosphates and pyrethroids have led to dissemination of resistance. Although these insecticides have been employed for decades against Aedes aegypti in the country, knowledge of the impact of temephos resistance on vector viability is limited. We evaluated several fitness parameters in two Brazilian Ae. aegypti populations, both classified as deltamethrin resistant but with distinct resistant ratios (RR) for temephos. The insecticide-susceptible Rockefeller strain was used as an experimental control. The population presenting the higher temephos resistance level, Aparecida de Goiânia, state of Goiás (RR95 of 19.2), exhibited deficiency in the following four parameters: blood meal acceptance, amount of ingested blood, number of eggs and frequency of inseminated females. Mosquitoes from Boa Vista, state of Roraima, the population with lower temephos resistance level (RR95 of 7.4), presented impairment in only two parameters, blood meal acceptance and frequency of inseminated females. These results indicate that the overall fitness handicap was proportional to temephos resistance levels. However, it is unlikely that these disabilities can be attributed solely to temephos resistance, since both populations are also resistant to deltamethrin and harbour the kdr allele, which indicates resistance to pyrethroids. The effects of reduced fitness in resistant populations are discussed.


Subject(s)
Animals , Female , Male , Aedes/drug effects , Genetic Fitness/drug effects , Insect Vectors/drug effects , Insecticides/pharmacology , Temefos/pharmacology , Aedes/physiology , Biological Assay , Brazil , Dose-Response Relationship, Drug , Insecticide Resistance , Insect Vectors/physiology
2.
Mem. Inst. Oswaldo Cruz ; 104(1): 43-47, Feb. 2009. ilus, graf, tab
Article in English | LILACS | ID: lil-507205

ABSTRACT

The control of Aedes aegypti is impaired due to the development of resistance to chemical insecticides. Insect Growth Regulators (IGR) exhibit distinct mechanisms of action and are considered potential vector control alternatives. Studies regarding the effects of sublethal IGR doses on the viability of resulting adults will contribute to eval-uating their impact in the field. We analyzed several aspects of Ae. aegypti adults surviving exposure to a partially lethal dose of triflumuron, a chitin synthesis inhibitor. A highly significant difference in the proportion of males and females was noted in the triflumuron-exposed group (65.0 percent males) compared to the controls (50.2 percent males). Triflumuron affected adult longevity, particularly for females; after 16 days, only 29.2 percent of males and 13.8 percent of females were alive, in contrast with 94 percent survival of the control mosquitoes. The locomotor activity was reduced and the blood-feeding ability of the treated females was also affected (90.4 percent and 48.4 percent of the control and triflumuron-exposed females, respectively, successfully ingested blood). Triflumuron-surviving females ingested roughly 30 percent less blood and laid 25 percent fewer eggs than the control females. The treated males and females exhibited a diminished ability to copulate, resulting in less viable eggs.


Subject(s)
Animals , Female , Male , Aedes/drug effects , Benzamides/pharmacology , Chitin/antagonists & inhibitors , Insecticides/pharmacology , Chitin/biosynthesis , Feeding Behavior/drug effects , Longevity/drug effects , Ovum/drug effects , Sexual Behavior, Animal/drug effects
3.
Rio de Janeiro; s.n; mar. 2007. xi,92 p. ilus, tab, graf.
Thesis in Portuguese | LILACS | ID: lil-464438

ABSTRACT

Aedes aegypti, Aedes albopictus e Culex quinquefasciatus são 3 espécies de mosquito difundidas principalmente nas regiões tropicais e subtropicais do globo. No Brasil, estão relacionadas com a transmissão de doenças como a dengue e a filariose linfática e há grande preocupação com sua potencial participação na transmissão de outras arboviroses, como o vírus do oeste do Nilo e o da febre amarela. Atualmente, a principal forma de combate a vetores de doenças é realizada através do uso de inseticidas químicos, cujo sítio de ação é o sistema nervoso central do inseto. Como conseqüência do uso maciço destes produtos, a freqüência de indivíduos resistentes em populações de várias espécies de insetos vetores tem aumentado. Os reguladores do desenvolvimento de insetos aparecem como uma nova alternativa de controle de mosquitos vetores. Neste grupo, encontram-se os inibidores da síntese de quitina (CSI), substâncias que prejudicam o processo de muda, acarretando deficiências principalmente na cutícula dos insetos. No presente trabalho, verificou-se que o CSI triflumuron foi eficaz contra estas 3 espécies de culicídeos vetores, em concentrações na ordem de (miu)g/L. Além disso, foi investigado o efeito da aplicação, em larvas, de dose parcialmente letal de triflumuron sobre vários aspectos da biologia de Ae. aegypti. De modo geral, a longevidade, aceitação do repasto sangüíneo, volume de sangue ingerido, reprodução e postura são afetados negativamente nos adultos sobreviventes ao tratamento na fase imatura. Triflumuron foi eficaz contra diversas populações de campo de Ae. aegypti, com diferentes níveis de susceptibilidade ao organofosforado temephos e ao piretróide deltametrina: não houve emergência de adultos viáveis quando as larvas foram expostas à IE99 de triflumuron para a cepa-referência Rockefeller. Embora não tenha sido detectada resistência cruzada entre aqueles inseticidas químicos e o CSI, a mortalidade de populações resistentes ao temephos, mas não à deltam...


Subject(s)
Animals , Chitin Synthase , Culicidae/parasitology , Vector Control of Diseases , Brazil
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